Scientists report COVID-19 reinfection cases, casting doubt on virus immunity

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In a new study, researchers found that COVID-19 patients may experience more severe symptoms the second time they are infected.

The finding confirms it is possible to catch the potentially deadly disease more than once.

The team reported the first confirmed case of COVID-19 reinfection in the United States—the country worst hit by the pandemic—and indicates that exposure to the virus may not guarantee future immunity.

The patient, a 25-year-old Nevada man, was infected with two distinct variants of SARS-CoV-2, the virus that causes COVID-19, within a 48-day time frame.

The second infection was more severe than the first, resulting in the patient being hospitalized with oxygen support.

The researchers noted four other cases of reinfection confirmed globally, with one patient each in Belgium, the Netherlands, Hong Kong, and Ecuador.

Researchers suggest that the prospect of reinfection could have a profound impact on how the world battles through the pandemic.

The team says the possibility of reinfections could have significant implications for our understanding of COVID-19 immunity.

Scientists need more research to understand how long immunity may last for people exposed to SARS-CoV-2 and why some of these second infections, while rare, are presenting as more severe.

The team says the US patient could have been exposed to a very high dose of the virus the second time around, triggering a more acute reaction.

Alternatively, it may have been a more virulent strain of the virus.

Another hypothesis is a mechanism known as an antibody-dependent enhancement—that is, when antibodies actually make subsequent infections worse, such as with dengue fever.

The researchers pointed out that reinfection of any kind remains rare, with only a handful of confirmed cases out of tens of millions of COVID-19 infections globally.

However, since many cases are asymptomatic and therefore unlikely to have tested positive initially, it may be impossible to know if a given COVID-19 case is the first or second infection.

One author of the study is Mark Pandori from the Nevada State Public Health Laboratory.

The study is published in The Lancet Infectious Diseases.

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